1. Field of the Invention
This invention relates to surface cleaning equipment, and more particularly to a surface blasting apparatus which recovers substantially all of the blasting abrasive utilized in the blasting operation, and cleans that abrasive of debris which is picked up from the treated surface. The invention further relates to surface blasting apparatus having interchangeable blasting heads of varying width and/or containing variously configured blasting wheels to accommodate the apparatus to varying blasting requirements.
2. Brief Description of the Prior Art
Many types of blasting machines utilizing shot or other small abrasive particles for cleaning a surface, followed by recovery of the abrasive and debris from the treated surface, have heretofore been proposed, and several types of such machines have been placed in commercial use. Many of the machines separate the dirt and debris from the abrasive, so that the cleaned abrasive can be reused. Some of such surface blasting machines employ a mechanical pick-up system to pick up the abrasive from the treated surface, and then use a conveying system to carry the abrasive back to an abrasive storage hopper.
Different methods are employed in these blasting machines to clean the abrasive to permit its re-use without the necessity to frequently interrupt the surface blasting. One method involves the utilization of an air wash which entails the passage of a rapidly moving jet or stream of air through a falling curtain of abrasive so as to blow the dust and debris, which is relatively lighter than the abrasive, away from the abrasive, and collect it in an isolated location. Most systems of this type with which I am familiar do not provide adequate cleaning of the abrasive in that small and greasy particles of debris still continue to adhere to, and build up on, the abrasive. Frequent machine stoppage to manually clean the abrasive is therefore still required.
Another problem which is characteristic of many types of air blast cleaning systems is that the air which is used to clean up the abrasive particles is discharged from the machine is a condition in which it still contains an undesirable amount of dust, thus contaminating the environment, and endangering the health and well being of the operator of the machine, as well as passers-by or onlookers.
Surface blasting machines which employ abrasive particles propelled against the surface to be cleaned by a rapidly rotating blasting head have also lacked optimum flexibility in terms of the utilization of a single machine where there are different requirements of blasting area, blasting depth and/or speed of blasting encountered from one job to another. Thus, a particular machine may be ideal for blasting a very narrow band along a highway, such as that which is developed when a thin line or stripe, such as a center line or lane stripe, is removed, but it may be inadequate for rapidly abrading a bridge deck, or the total transverse width of a highway, at a rate which is competitive with some other types of blasting machines. The narrow blasting head which delivers optimum performance in removing stripes or painted bands is not adequate to permit a rapid speed of advance where the machine is to abrade a larger area of surface. Instead, it is often necessary to use two different types of machines for these two different types of job requirements, and an operator or contractor may be undesirably delayed in changing machines for the different job requirements. In some instances, both types of machines as needed for both of these kinds of jobs may not be readily available to the contractor.
Another problem which is encountered during the use of some types of surface blasting apparatus occurs where a relatively narrowly dimensioned blasting head is employed to remove the median stripe or lane lines from a highway surface. This problem is the propensity of machines presently available to trench or groove the highway during the stripe removal procedure. This result occurs because the relatively narrow blasting head channels and directs the abrasive particles into a highly concentrated, relatively small transverse width dimension, and the high concentration of high velocity abrasive particles develops a gouging or digging action which leaves an undesirable depression at the location where the stripe or lane line previously existed but has now been removed.
Some of the machines of the type described which have previously been proposed are depicted in U.S. Pat. No. 4,376,358 to Shelton, U.S. Pat. No. 4,382,352 to Nelson, U.S. Pat. No. 4,020,596 to Bergh, U.S. Pat. No. 4,416,092 to Nelson, U.S. Pat. No. 4,364,823 to Goff, U.S. Pat. No. 4,433,511 to Swain, U.S. Pat. No. 3,691,689 to Goff, U.S. Pat. No. 3,900,969 to Diehn, U.S. Pat. No. 3,877,175 to Snyder, U.S. Pat. No. 3,934,373 to Leliaert, U.S. Pat. No. 4,364,823 to Bergh, U.S. Pat. No. 4,336,671 to Nelson, U.S. Pat. No. 3,858,359 to Leliaert, U.S. Pat. No. 4,052,820 to Bergh, U.S. Pat. No. 4,377,924 to Bergh, U.S. Pat. No. 3,977,128 to Goff, U.S. Pat. No. 3,756,377 to Goff, U.S. Pat. No. 4,377,922 to Bergh, United Kingdom Patent Application No. 2,072,549, European Patent Application No. 0,032,161 and U.S. Pat. No. 4,377,923 to Bergh.
The surface blasting apparatus of the present invention provides a means for adequately air cleaning the abrasive particles, and for filtering the dust and debris from the cleaning air stream before discharging it to the atmosphere. The apparatus also offers a very versatile, utilitarian machine which, by the use of interchangeable blasting heads mounted on a common framework, can be used to meet varying specialized usage requirements, such as removing a narrow stripe from a highway or parking lot surface, or blasting a much wider path in a relatively high speed fashion to permit a large surface area to be cleaned in a short period of time. The apparatus also permits a narrow stripe to be removed from the highway without grooving the highway excessively during such removal.